为提高消光椭偏测量技术的测量精度,提出了一种基于光弹调制的消光椭偏测量技术。将光弹调制器和两块λ/4波片组合构成旋光调制器,对相关方位角进行调制。通过测量基频分量消光时的起偏器和检偏器的方位角,完成对椭偏参量的测量。与传统消光椭偏测量技术相比,该技术消除了背景噪声和环境干扰等对测量结果的影响。利用琼斯矩阵分析了该椭偏测量技术的原理,最后利用ZnS薄膜验证了基于光弹调制的消光椭偏测量技术的可行性。

In order to improve the measurement accuracy of null ellipsometry,a null ellipsometry based on photoelastic modulation is presented. Azimuth modulation is achieved through a photoelastic modulator and two quarter-wave plate. The ellipsometric parameters are obtained by azimuth measurement of the polarizer and analyzer,for which the first harmonics of modulator frequency cross the zero. Comparing with traditional null ellipsometry,it can eliminate the effect of background noise and environmental disturbance. The measurement principle is analyzed by using Jones matrix. With measured thickness and optical parameters of ZnS film,the feasibility of the null ellipsometry based on photoelastic modulation is thus demonstrated.